A parallel link robot is a robot in which a plurality of link portions are arranged between abase and a movable portion. By driving the plurality of link portions with the plurality of actuators, a position or a position and an attitude of the movable portion is/are changed. As types of the parallel link robot, there are an extendable parallel link robot, a rotary parallel link robot, and a linear parallel link robot.
The extendable parallel link robot was proposed the earliest and is used for aircraft simulators, play facilities, and the like. The extendable parallel link robot is formed by arranging six extendable links between a base and a movable portion. By changing link lengths of the extendable links, the movable portion is caused to perform translational movements in directions of three axes, i.e., an x-axis, a y-axis, and a z-axis and an attitude of the movable portion is caused to rotate about the three axes, i.e., the x-axis, the y-axis, and the z-axis (refer to Patent Literature 1).
For the rotary parallel link robot, rotary actuators are used as drive sources. As a typical example of the rotary parallel link robot, there is a known device in which a base is formed in a triangular shape, three motors are mounted to respective sides of the triangular shape of the base in such a manner that output shafts of the motors are parallel to the respective sides, thin and long arms rotating about the output shafts of the respective motors are integrally connected to the output shafts, and tip ends of the respective arms and the movable portion are connected by links (refer to Patent Literature 2). By driving the three arms connected to the output shafts of the three motors for rotation, the movable portion is caused to perform translational movements in directions of three axes, i.e., an x-axis, a y-axis, and a z-axis relative to the base. If six motors, arms, and links are provided, it is possible to achieve not only the translational movements of the movable portion in the directions of the three axes, i.e., the x-axis, the y-axis, and the z-axis but also rotation of an attitude of the movable portion about the three axes, i.e., the x-axis, the y-axis, and the z-axis.
For the linear parallel link robot, linear actuators are used as drive sources. As a typical example of the linear parallel link robot, there is a known mechanism in which six guides are radially fixed to a base at predetermined angles, sliding tables to be driven by ball screws are mounted to the respective guides to be able to move linearly, and the sliding tables of the respective guides and the movable portion are connected by rods (refer to Patent Literature 3). By linearly moving the sliding tables of the six guides, the movable portion can be caused to perform translational movements in directions of three axes, i.e., an x-axis, a y-axis, and a z-axis and an attitude of the movable portion can be changed about the three axes, i.e., the x-axis, the y-axis, and the z-axis.